What the Heck is this?

[JamesG161]

It is an adapter that screws to a quart of gear lube. The yellow and black sections twist to turn the flow off/on. This way you can put the hose in the filler hole and then open the flow of lube.

Where I found it was near the genset and the inside of the tubing was not oily but looked like dries salt water.
On yours, do you have a "quick disconnect" on left/white piece?
Jim...

 

[JerryA]

No disconnect on mine. Yours was added. The white end screws onto a bottle. The twist valve works pretty well, so it could be used for just about any use where you need to turn on/off the flow of a fluid.

JerryA

 

[bawlmer]

Maybe it is a backflow preventer. Something that allows water to flow one way amd not the other. That may account for the arrow. I had to use one for my irrigation at a previous house I used to reside in.

 

[JamesG161]

Well avoiding all the storms on the weekends, I finally got to search and the boat. I found only a back up spare.

he assembled a do-hicky.

The do-hicky is the twist open/shut valve as many noted.
But...
I never found the gozinta black end mating piece. The dangley tubie on the yellow Wachamycallit showed no oily stuff.

I owe the following a plethora of Greek...

the craft beer

@Gunni , @centerline , @JerryA , @woodster BTW...

The PO cross threaded the gozinta in the white thingy and therefore he needed a spare.
Thanks all...
Jim...

PS: @Gunni gets the innovation prize for....

your wash-down pump intake it would provide the ability to use your wash-down as a bilge pump.